What is the correct belt tension on swamp cooler motor?

Master Cool II uses a 59 inch belt between motor and fan pulley. The setup instructions say to leave 1/2 to 3/4 inch of slack when pressing on the belt at its midpoint between pulleys. When I first installed the unit the motor kept cutting out. This is due to a temperature cutoff switch that turns the motor off when it gets too hot. To get it right I used an inductive ac ammeter (borrowed from work) to adjust the belt tension until the motor draws the correct number of amps as stated on the motor faceplate. Today I installed a new fan belt. I began by marking the position bracket of the fan motor with a pencil. I put the new belt on with the motor bracket in the marked position. The fan cutout in ~15 minutes. I loosened the belt some and it cut out in ~20 minutes. I loosened it still more and it is now working properly. Master Cool II uses a 59 inch belt between motor and fan pulley. The setup instructions say to leave 1/2 to 3/4 inch of slack when pressing on the belt at its midpoint between pulleys. When I first installed the unit the motor kept cutting out. This is due to a temperature cutoff switch that turns the motor off when it gets too hot. To get it right I used an inductive ac ammeter (borrowed from work) to adjust the belt tension until the motor draws the correct number of amps as stated on the motor faceplate. Today I installed a new fan belt. I began by marking the position bracket of the fan motor with a pencil. I put the new belt on with the motor bracket in the marked position. The fan cutout in ~15 minutes. I loosened the belt some and it cut out in ~20 minutes. I loosened it still more and it is now working properly.